Electric stove



April 29, 1930. c. 'c. ARMSTRONG ELECTRIC STOVE Original Filed Aug. 3, 1925 Ck axle.- C. Arm-227201190 Patented Apr. 29, 1930 UNITED STATES PATENT OFFICE CHARLES C. ARMSTRONG, OF HUNTINGTON WEST VIRGINIA, ASSIGNOR'TO THE ARM- STRONG ELECTRIC AND MANUFACTURING CORPORATION, A CORPORATION OF DELAWARE ELECTRIC STOVE Original application filed August 3, 1925, Serial No. 47,830. Divided and. this application filed February 18, 1928, Serial No. 255,423.

The invention disclosed herein is a division of the subject matter disclosed in my application filed Feb. 3, 1927, Serial No. 165,676, which is a division of the subject matter disclosed in my application filed Aug. 3, 1925, Serial No. 47830.

The invention relates to the thermostat for controlling the temperature of the oven of the electric stove and consists in the features, combination, and arrangement of parts hereinafter described and particularly pointed out in the claims.

In the drawings Figure 1 is a vertical fragmentary section of the stove from front to rear showing the thermostat control device mounted in the hinged front door of the stove, openings being provided in the three plates of the front door to receive the thermostat mechanism.

Fig. 2 is a horizontal sectional view of the thermostat organization.

Fig. 3 is a front view.

Figs. 4, 5, 6, 7, 8 and 9 are views of details.

Referring to the drawings, the stove door 27 in which the thermostat is mounted is hinged at its lower edge to the front body panel 25 at 35 and it is composed of a front portion or panel 27 a back 341 and an intermediate member 34". These members of the door are held together by their interlocking flanges at 3a and by male and female screws 34* which connect the door members 27*, 27 34 and 34 to make a rigid door structure. A door of the construction described provides two dead air spaces one on each side of the centralplate or member 8a and these spaces provide heat insulation at these points.

The thermostat for controlling the temperature of the oven is mounted in the hinged front door.

Openings are provided through the three plates or members of the front door to receive the thermostat mechanism. In the opening in the back sheet metal plate 34*, Fig. 2, a cup shaped shell t is mounted by the contacting flanges thereof engaging the flange t of the door member, screws t holding the shell in place. i The open side of this cup member+ communicates with the oven Renewed March'4, 1930.

space and consequently is exposed to the oven temperature. Within this cup shaped memher is located the thermostat coil 6 the outer end of this coil being attached to the wall of this cup shaped shell for which purpose the shell has an inwardly extending lug t" struck out therefrom which is engaged by the end of the coil, which is slotted at t to receive the lug. j

The inner end of the coil extends diametrically thereof and through a slot t in the center shaft 2& where it is held by a screw 6 threaded into the shaft coaxially therewith and engaging a notch in the edge of the strip of metal forming the coil. The coil encircles asheet metal cup shaped shell i which is held to the shaft by the same screw t which serves to hold the inner end of the'coil to the center shaft. This shell is slotted at t for the passage of the coil. It is provided with projections 13 which enter the slot t of the shaft and hold it against circumferential displacement relative to the shaft.

This shaft i has a bearing in the shell t and in a sheet metal shell t which is flanged and is secured to the plate or member34 of the front door by a spacer 25 extending between the walls 34 and 84t of the door.

A screw t extends through thespacer and is threaded into a screw 10, the head of which bears on the outer side of the front wall or member of the door structure. Threaded on the screw 25 are nuts 25 one of which bears on the outer face of the intermediate plate 34* of the door. Between these nuts the insulated electric terminal i of the thermostat is clamped. This construction t 23 etc. is duplicated at the other side of the thermostat organization. The shell 25 closes the flanged opening in the intermediate member or plate 34* of the door structure andthere is a dead air space between this shell and the cup 25 inlwhich latter the thermostat coil is located so that thermal insulation is'secured at this point insuring that the thermostat coil will be subjected only to the temperature within the oven. The shaft t is shouldered at'its outer end and on the reduced end thus provided i'smounted a holder 25 for the mercury tube 25 which has within it the electric v at) a position contacts which are closed and opened by the mercury according to whether the position of the tube is such as to immerse the contacts or to flow the mercury away therefrom. This mercury tube holder is mounted frictionally on the shaft by a screw and spring the shaft 25 in one direction or the other according as the temperature rises or falls. The tube holder has an arm 25 with a pointer thereon to move over a scale 25. This scale is marked on a stamped sheet metal shell provided with ears overlying and screwed to the outer surface of the front wall of the door.

There is a space or slot between the edge of the scale member and the edge of the door plate as shown at Z and the arm t extends out through this slot or space, where it is accessible for setting by the cook.

Fixed to the shaft 2i there is an indicator arm t. This has an opening to fit the reduced end of the shaft with projections W to fit a kerf in this reduced shaft end wherein the projections are held because the hub portion of this arm underlies the hub portion of the tube holder which as above stated is frictionally held by the spring washer and screw.

This indicator arm works over a scale It marked on the same plate with the scale 6, but in the opposite direction.

The contact points carried within the mercury tube are shown at 25 and electrical connection is made to these points from the terminals i above described.

In setting the thermostat for any desired temperature the indicator pointer is held or moved to the scale mark 1 on its scale 17 and while it is held in this position the pointer t' of the mercury tube holder is moved on its scale to the point or scale mark indicating the temperature desired. This latter action of course will set the holder in relation to the shaft 5* and the indicator pointer. Then rclease the indicator pointer and allow the instrument to assume its position according as the temperature of the coil will call for at this moment. Now when the indicator hand under a rise in temperature reaches the mark on its scale corresponding to the mark at which the pointer of the mercury tube holder was initially set in making the setting or adjustment, the mercury tube will have reached at which it will be so inclined that the mercury will flow away from the contact points leaving them bare and thus the current to the actuating coil of the relay switch will be broken and the current to the heating element will be cut off and remain so until the temperature within the oven falls below that for which the instrument is set, wl ere upon the contraction of the coil will turn the shaft t the other way and. by carrying the mercury tube holder along with it the latter will be inclined the other way so that the mercury will flow to the end of the tube at which the electrical contacts are located, causing their immersion and electrical connection and the current will therefore be supplied again to the heating elements.

The various shells above described, the tube holder, the indicator arm, the spring washer, and the terminals t are all of stamped sheet metal. The tube holder has besides its arm t and the hub portion, a pair of arms t which have sulficient spring action to grip the tube and hold it in place.

The general construction of the thermostat organization lends itself to association with the construct-ion of the door above described, and the feature relating to heat insulation is carried out in connection with this thermostat organization.

I claim V 1. In combination with a thermostatic member, a shaft having a shoulder, a sheet metal member, a spring washer and screw for holding said member frictionally in connection with said shoulder, spring arms on said sheet metal member, a mercury tube carried by said spring arms, an indicator arm of said sheet metal member, an indicator arm of sheet metal havin projections at its opening for engaging a kerf of said shaft and a scale over which the arms move, substantially as described.

2. In combination in a thermostat, a shaft thermally controlled to rotate under temperature variations, an electric switch carried by said shaft and. adjustable to different positions about the same to change the point of operation of the switch according to the degree of heat desired, an indicator connected to and adjustable with said switch, a scale over which said indicator moves, a second indicator fixed to said shaft and a scale over which said latter indicator moves to indicate the degree of heat to which the thermostat is subj ected, substantially as described.

3. In combination in a thermostat, a shaft, a thermal element connected thereto to rotate said shaft under variations of temperature, a mercury tube carrying circuit making and breaking means held to said shaft to be adusted about the same, an indicator, and scale for setting said mercury tube according to the degree of heat at which the circuit is to be broken, and an indicator fixed to said shaft with a scale therefor ,to indicate the degree of heat to which the thermostat issubjected, said thermostat being set for the prescribed degree of heat by moving the last named indicator to the beginning of its scale and while maintaining said indicator in this position moving the first named indicator with the mercury tube about said shaft and to that part of the scale corresponding to the desired degree of heat and thereafter releasing said indicators to allow the shaft to assume a position according to the degree of heat to which said thermostat is then subjected.

4. In combination in a thermostatically operated switch, a shaft, a thermal element connected to the shaft for rotating the same, a mercury tube switch frictionally mounted on said shaft, an indicator arm connected with said mercury tube and movable therewith, a scale over which said arm is adapted to move, and means for determining the initial position of said shaft and thermostat, and whereby the shaft may be held in said initial position while the indicator arm of the mercury tube is set relative to the scale and shaft for the degree of heat at which the circuit is desired to be broken and thereafter releasing the shaft and arm.

5. In combination with a thermostat. a shaft controlled by said thermostat to rotate under temperature variations, an electric switch carried by said shaft and adjustable to different positions about the shaft to change the point of operation of the switch according to the degree of heat desired, an indicator connected to and movable with said switch, a scale over which said indicator moves, means for determining the initial position of said shaft and thermostat and whereby the shaft may be held in said initial position while the indicator arm of the mercury tube is set relative to the scale and shaft for the degree of heat at which the circuit is'desired to be broken and thereafter releasing the shaft.

said latter indicator moves to indicate the degree of heat to which the thermostat is subjected, the first mentioned scale running clockwise and that last mentioned running anticloclm'ise about the axis of the shaft and located on opposite sides of said shaft, substam tially as described.

7. In combination in a thermostat, a shaft thermally cont-rolled to rotate under temperature variations, an electric switch carried by said shaft and adjustable to different positions about the same to change the point of operation of the switch according to the Ge gree of heat desired, an indicator connected to and adjustable with said switch, a scale over which said indicator moves, a second indicator fixed to said shaft and a scale over which said latter indicator moves to indicate the degree of heat to which the thermostat is subjected, the first mentioned scale running in one direction and that last mentioned running in the opposite direction about the axis of the shaft and located on opposite sides of the shaft, substantially as described.

In testimony whereof, I affix my signature.

CHARLES C. ARMSTRONG. 

